Reforming with halogen promoted platinum-alumina catalyst alone or with metal promoters to form a bimetallic reforming catalyst now constitutes one of the major petroleum processing routes for upgrading naphtha boiling-range fractions to higher octane gasoline product. With a need to process relatively large volumes of naphthas, maintaining hydrogen purity of the reformer recycle gas in combination with gains in reformate product yield permits substantial savings in operating costs. A reformate yield improvement of only 0.5% by volume represents annual savings of several million dollars to the refining industry. However, to achieve these savings, it is important to charge clean naphthas of low sulfur and nitrogen content. The present invention is concerned with improving desulfurization of a naphtha fraction charged to a reforming operation whether employed in a regenerative, semi-regenerative or non-regenerative type reforming operation. In yet another aspect, the present invention is concerned with desulfurizing a wide boiling range sulfur containing naphtha fraction under conditions providing a desulfurized naphtha containing less than 0.5 ppm of sulfur and preferably not more than about 0.2 ppm of sulfur.
The combination of hydrogenative desulfurization of naptha containing material, separation of C.sub.5.sup.- material including sulfur containing material and effecting catalytic reforming of the desulfurized naphtha with and without bimetallic reforming catalyst is known and disclosed in the prior art. Also effecting the reforming operation in the presence of selected amounts of water vapor, halogen addition and selectively presulfiding highly active fresh catalyst initially to restrict undesired hydrocracking activity of the catalyst is discussed at length in the prior art. Some U.S. patents particularly so directed include: U.S. Pat. Nos. 3,110,703; 3,193,495; 3,374,026; 3,415,737; 3,449,237; 3,562,147; 3,661,768; and 3,649,524.